Experiment with Plums with this Midwestern-style Umeboshi

We got some greengage plums in, and they made me start thinking about umeboshi and umeboshi vinegar. Both are great, but I wanted to do something more than just try to make umeboshi or vinegar. I can’t buy the traditional ume (used to make umeboshi in Japan); they are too expensive by the time they are imported here. And aside from that, I don’t even know...